On your smartphone, you’re not much more than a data machine, generating reams of valuable information that tech companies can mine for insights, sell to advertisers and use to optimize their products.

The internet has upended many trades. Next, perhaps, will be census takers. A new study finds that Google’s “Street View” photographs can be used to estimate a neighborhood’s racial fabric. They can also correctly predict if a town will vote Democrat or Republican over 80 percent of the time.